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Clouds may be absorbed into the atmosphere 

 or evaporated and become invisible; and 

 this process is going on to a greater or less de- 

 gree continually. If we watch the steam as it 

 escapes from a steam boiler, the first effect is 

 condensation into cloud, but as it floats away 

 it gradually melts and is absorbed into the at- 

 mosphere as invisible vapor. This is espe- 

 cially true on a warm day; the same process 

 takes place in the air that is going on at the 

 level of a body of water or at the surface of 

 moist earth. 



As before stated, condensation always takes 

 place when a body of moisture-laden air comes 

 in contact with cold. When the steam escapes 

 from a boiler, even on the hottest day, it is 

 hotter than the surrounding air; the first 

 effect is condensation, and then evaporation 

 takes place the same as it would at the surface 

 of the earth when the condensed particles of 

 moisture are separated into the invisible atoms 

 that accompany evaporation. 



In settled, dry weather as the sun ap- 

 proaches the zenith, the earth becomes in- 

 tensely heated, and there is an ascending 

 column of air partly laden with moisture; but 

 not to the same extent as earlier in the season. 

 Condensation takes place and clouds are 

 formed, but as there is not sufficient moisture 

 to carry them to the point of a further conden- 

 sation, which would result in precipitation, 



